A polyolefin blending technique is a technique of directly melting and blending compatible homopolymer/homopolymer, homopolymer/copolymer, or copolymer/copolymer to product a polymer alloy. An in-reactor polyolefin alloy is a polyolefin alloy obtained directly from reacting monomers through in-reactor polymerization. That method replaces the traditional blending method that melts and blends polymer components in the prior art. Among in-reactor polyolefin alloys, the most common in-reactor polyolefin alloy is in-reactor polypropylene alloy, which is usually produced by forming propylene into porous polypropylene particles through polymerization in the presence of a olefin polymerization catalyst and then charging a comonomer of ethylene and α-olefin into the polymerization system to perform a copolymerization reaction in the porous polypropylene particles so that the elastic copolymer generated fills up the voids among the porous polypropylene particles.
In recent years, though the olefin polymerization modifiers that have new structures and new features have been discovered and applied in researches for improving the performance of in-reactor polyolefin alloys continuously, effective catalytic polymerization means for preparing some high-performance in-reactor polyolefin alloys that have wide application prospects are still inadequate. For example, polypropylene-based thermoplastic elastomers (Thermoplastic Dynamic Vulcanizate, TPV) in which the rubber phase is in a crosslinked structure have outstanding mechanical properties and high added values, and have wide application prospects in high-end application domains. However, the existing TPV products are mainly obtained through modification processes after polymerization (dynamic vulcanization and crosslinking). There is no report on preparation of TPV through a polymerization process.
Making the rubber phase crosslinked through polymerization has advantages in many aspects: 1.) a complex post-modification process is omitted, and the increased cost incurred by the process is eliminated; 2.) the in-reactor crosslinking technique has characteristics including controllable degree of crosslinking and more diversified products, and thereby a series of in-reactor polyolefin alloys, such as in-reactor polyolefin alloys with high rubber content (rubber mass percent is 50 mass % or higher), high impact-resistant in-reactor polyolefin alloys, and polypropylene-based thermoplastic elastomers (TPV) which rubber phase is in a crosslinked structure, etc., can be prepared in a controlled manner by adjusting the kind of crosslinking monomer and addition amount; 3) the dependency on the polymerization catalyst and the polymerization process is lower.
Content of the Invention
The present invention is to provide a use of organosilane in preparation of an in-reactor polyolefin alloy, a method of preparing an in-reactor polyolefin alloy, and an in-reactor polyolefin alloy prepared by the method.
Specifically, the present invention provides a use of organosilane in preparation of an in-reactor polyolefin alloy, wherein the organosilane is represented by a general formula R1mSiXn(OR2)k, wherein R1 is a C2-C20 alkyl group and a terminal of R1 has an α-olefin double bond, a norbornene group, a cycloolefin group or a dicyclopentadiene group, X is a halogen element, R2 is a C1-C20 linear chain, branched chain or isomerized alkyl group, m is an integer within a range of 1-3, n is an integer within a range of 1-3, k is an integer within a range of 0-2, and m+n+k=4.
The present invention further provides a method of preparing an in-reactor polyolefin alloy comprising: conducting the first polymerization reaction of the first olefin monomer in the presence of a catalyst, and then charging the second olefin monomer into the polymerization reaction system to perform the second polymerization reaction, wherein the first olefin monomer is different from the second olefin monomer, wherein the first polymerization reaction and/or the second polymerization reaction are/is executed in the presence of organosilane represented by a general formula R1mSiXn(OR2)k, wherein R1 is a C2-C20 alkyl group and a terminal of R1 has an α-olefin double bond, a norbornene group, a cycloolefin group or a dicyclopentadiene group, X is a halogen element, R2 is a C1-C20 linear chain, branched chain or isomerized alkyl group, m is an integer within a range of 1-3, n is an integer within a range of 1-3, k is an integer within a range of 0-2, and m+n+k=4.
Furthermore, the present invention further provides an in-reactor polyolefin alloy obtained by the above-mentioned method.
Through in-depth research, the inventor of the present invention has found that the organosilane represented by the general formula R1mSiXn(OR2)k behaves quite differently from the organosilane represented by a general formula Si(OR′)4 (wherein R′ is a C1-C20 alkyl group) and the organohalosilane represented by a general formula SiX′4 (wherein X′ is a halogen element) during the in-reactor polyolefin alloy preparation process. If the first and/or the second polymerization reaction in the in-reactor polyolefin alloy preparation process are executed in the presence of the organosilane represented by the general formula R1mSiXn(OR2)k, the degree of crosslinking of the rubber phase in the obtained in-reactor polyolefin alloy is higher, and the in-reactor polyolefin alloy has higher impact toughness and lower tensile breaking strength.
According to the preferred example of the present invention, if the R1 in the organosilane is a C2-C20 alkyl group and a terminal of R1 has an α-double bond, a norbornene group, a cycloolefin group or a dicyclopentadiene group, X is a halogen element, R2 is a C1-C10 linear chain, branched chain or isomerized alkyl group, m is 2 or 3, n is 1 or 2, k is 0, and m+n+k=4, the rubber phase in the obtained in-reactor polyolefin alloy is crosslinked to a higher degree, and the in-reactor polyolefin alloy has higher impact strength and lower tensile breaking strength.
Other features and advantages of the present invention will be further detailed in the examples hereunder.